With prior art constant velocity universal joints of the tripode type, it is frequently the inner roller which guides the roller assembly in the guiding track. At the same time, the inner roller is frequently provided with axial securing means which, via a pressure disc, support the needle bearing and the outer roller, with the outer roller, at the inner end, being supported on a collar provided at this end. At the same time, the inner roller is supported inside the guiding groove on its radial outer wall in order to prevent the roller assembly from tilting (EP-OS 0426186). The disadvantage of the prior art design is that, because of its additional functions, the inner roller has a relatively great axial length. This axial length determines the height of the guiding groove, as a result of which the outer diameter of the outer joint part is rather great.
To provide the roller assembly with the necessary pivoting ability and thus to achieve a predetermined articulation angle, the neck of the arm is generally rather weak, which necessarily has a negative effect on the torque transmitting capacity.
It is the object of the present invention to increase the torque transmitting capacity of a constant velocity universal joint of the tripode type while retaining its size and especially to increase the strength of the region of transition from the inner joint part to the spherical arm.
It is also within the scope of the objective of the present invention to reduce the size of the joint while maintaining its torque transmitting capacity.
The objective is achieved in that each outer roller, at its axially outer end with reference to the axis of the spherical arm, comprises a radially inwardly pointing collar supporting the inner roller axially outwardly, that at the cylindrical inner wall of the outer roller there is arranged axially inner axial securing means supporting the inner roller via a pressure disc axially inwardly, and that the neck of the inner joint part, starting from the hub of the inner joint part, extends generally tangentially from the hub continuously towards the spherical arm with an ever decreasing ovaloid shape, with no necking being provided in the region of transition from the neck to the spherical arm.
By arranging the axial securing means at the inner wall of the outer roller and by positioning them at the outer roller end facing the joint axis, it is possible to considerably shorten the length of the inner roller and also of the associated needle beating.
As in this case parallel alignment of the roller assembly is entirely effected by the outer roller and as the axial securing means are still located in the guiding region of the outer roller, it is possible to considerably shorten the roller assembly in the radial direction with reference to the joint axis.
As a result of the short design of the inner roller, it is possible to provide the region of transition from the hub of the inner joint part to the spherical arms, i.e. the so-called neck, with a much greater thickness, which results in an increase in the torque transmitting capacity of the constant velocity universal joint.
According to a further embodiment of the invention it is proposed that, in the circumferential direction, the neck of the spherical arm should feature a greater resistance moment than in the axial direction.
This measure results in an additional increase in the torque transmitting capacity.
Furthermore, because of the axially outer collar, with reference to the axis of the spherical arm, the outer roller is provided with an increased resistance moment, as a result of which the circumferential force is distributed more effectively to the largest possible number of bearing needles.
According to an advantageous feature of the invention, the outer roller, with reference to the axis of the spherical arm, projects axially outwardly beyond the needle bearing and the inner roller merely by an amount corresponding to the thickness (h) of the collar.
This feature advantageously contributes towards reducing the outer diameter of the outer joint part.
In a further advantageous embodiment of the invention, the outer limiting faces of the guiding grooves, in each case, are provided with two bead-like stop faces arranged at a distance from the circumferentially extending guiding tracks and extending along the axial length of the guiding grooves.
This results in production-technical advantages because all radii can be kept relatively large, which means that both the broaching operation and the production of the outer joint part by a pressing process are simplified.
Furthermore, because there exists a defined contact line at the bead-shaped stop faces, the hardening operation may be limited to said stop faces.